# (TFT) Big Cidri

"In the Labyrinth" says that Cidri has 48 known continents, and many more land masses that are considered smaller than continents. There's good evidence that there are more continents than the known 48. It says that Cidri is about half land and half water. Every Cidri-based campaign that anyone ever mapped is on Cidri somewhere. Let's say 100 continents. The Earth has 149 million square kilometers of land, and we usually say we have 7 continents. Divide by 7 and multiply by 100, and you get 2,127,700,900 square kilometers of land area, and a total global surface area on Cidri of 4,255,401,800 square kilometers. If I did my sums right, that's a planet with about an 18,400 kilometer radius. With a similar density to Earth, that's 1.44 times ten to the 24th kilograms of mass. If I figured this right (a big "if,") Cidri would have a surface gravity about nine times that of Earth. The exotic anti-mass in the middle would have to push on people with eight gees upward acceleration to make it cancel out to earth-like gravity.

In physics class I learned that gravity cancels itself out inside a hollow sphere, so if the Earth were hollow, there'd be no gravity at all inside. In the hollow space around the anti-gravity ball, the only gravity you'd feel would be the anti-gravity. The "up" force from the ball would be stronger than on the surface because you'd be closer to it, so there'd be more than eight times Earth's gravity pushing you towards the surface.

If a mad Mnoren built the universe's deepest stairwell on Cidri, as you walked down and down, you'd feel the gravity get lighter. You'd eventually fly down the stairs in zero gravity. Then you'd be climbing up a staircase instead of going down, as the anti-gravity got stronger. Climbing those stairs would get harder as you got heavier, and heavier, and heavier.

The Cidri might have built big underground habitats at different levels under the surface. A low-gravity level would allow adventurers to jump around like John Carter of Mars. Deeper than that, you could have strange zero-gravity ecologies, as in Larry Niven's "The Smoke Ring." Deeper still, there'd be places for stocky little high-gravity beings. The dwarves of Cidri might be humanoids whose ancestors lived in higher gravity.

I can imagine a race of weird light-hating gravity-loving beings living on the inner surface of Cidri. If a scientist among them predicted a disaster that would wipe out all life on the inside, he might teleport his son to the surface. Perhaps the child would be taken in by kindly farmers. Little Kal would be fantastically strong, but he'd have to wear sunglasses. When he grew up, he could move a city and be a great hero.

--Scott
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